(function(factory){
    if(typeof define === 'function' && define.amd){
        define(['jquery'],factory);
    }else{
        factory(window.jQuery);
    }
}(function($){
        //参数
        var setting = {
                column_width: 300, //列宽
                column_className: 'waterfall_column', //列的类名
                column_space: 20, //列间距
                cell_selector: '.item', //要排列的砖块的选择器，context为整个外部容器
                img_selector: 'img', //要加载的图片的选择器
                auto_imgHeight: true, //是否需要自动计算图片的高度
                fadein: true, //是否渐显载入
                fadein_speed: 600, //渐显速率，单位毫秒
                insert_type: 1, //单元格插入方式，1为插入最短那列，2为按序轮流插入
                getResource: function(index) { }  //获取动态资源函数,必须返回一个砖块元素集合,传入参数为加载的次数
            },
            waterfall = $.waterfall = {}, //对外信息对象
            $container = null;//容器
        waterfall.load_index = 0, //加载次数
        $.fn.extend({
            waterfall: function(opt) {
                opt = opt || {};
                setting = $.extend(setting, opt);
                $container = waterfall.$container = $(this);
                waterfall.$columns = creatColumn();
                render($(this).find(setting.cell_selector).detach(), false); //重排已存在元素时强制不渐显
                waterfall._scrollTimer2 = null;
                $(window).bind('scroll', function() {
                    clearTimeout(waterfall._scrollTimer2);
                    waterfall._scrollTimer2 = setTimeout(onScroll, 300);
                });
                waterfall._scrollTimer3 = null;
                $(window).bind('resize', function() {
                    clearTimeout(waterfall._scrollTimer3);
                    waterfall._scrollTimer3 = setTimeout(onResize, 300);
                });
            }
        });
        function creatColumn() {//创建列
            waterfall.column_num = calculateColumns();//列数
            //循环创建列
            var html = '';
            for (var i = 0; i < waterfall.column_num; i++) {
                html += '<div class="' + setting.column_className + '" style="width:' + setting.column_width + 'px; display:inline-block; *display:inline;zoom:1; margin-left:' + setting.column_space / 2 + 'px;margin-right:' + setting.column_space / 2 + 'px; vertical-align:top; overflow:hidden"></div>';
            }
            $container.prepend(html);//插入列
            return $('.' + setting.column_className, $container);//列集合
        }
        function calculateColumns() {//计算需要的列数
            $container.css({width:'auto'});
            var num = Math.floor(($container.innerWidth()) / (setting.column_width + setting.column_space));
            if (num < 1) {
                num = 1;
            } //保证至少有一列
            $container.css({width:(num*(setting.column_width+20))+'px'});
            return num;
        }
        function render(elements, fadein) {//渲染元素
            if (!$(elements).length)
                return;//没有元素
            var $columns = waterfall.$columns;
            $(elements).each(function(i) {
                if (!setting.auto_imgHeight || setting.insert_type == 2) {//如果给出了图片高度，或者是按顺序插入，则不必等图片加载完就能计算列的高度了
                    if (setting.insert_type == 1) {
                        insert($(elements).eq(i), setting.fadein && fadein);//插入元素
                    } else if (setting.insert_type == 2) {
                        insert2($(elements).eq(i), i, setting.fadein && fadein);//插入元素
                    }
                    return true;//continue
                }
                if ($(this)[0].nodeName.toLowerCase() == 'img' || $(this).find(setting.img_selector).length > 0) {//本身是图片或含有图片
                    var image = new Image;
                    var src = $(this)[0].nodeName.toLowerCase() == 'img' ? $(this).attr('src') : $(this).find(setting.img_selector).attr('src');
                    image.onload = function() {//图片加载后才能自动计算出尺寸
                        image.onreadystatechange = null;
                        if (setting.insert_type == 1) {
                            insert($(elements).eq(i), setting.fadein && fadein);//插入元素
                        } else if (setting.insert_type == 2) {
                            insert2($(elements).eq(i), i, setting.fadein && fadein);//插入元素
                        }
                        image = null;
                    };
                    image.onreadystatechange = function() {//处理IE等浏览器的缓存问题：图片缓存后不会再触发onload事件
                        if (image.readyState == "complete") {
                            image.onload = null;
                            if (setting.insert_type == 1) {
                                insert($(elements).eq(i), setting.fadein && fadein);//插入元素
                            } else if (setting.insert_type == 2) {
                                insert2($(elements).eq(i), i, setting.fadein && fadein);//插入元素
                            }
                            image = null;
                        }
                    };
                    image.src = src;
                } else {//不用考虑图片加载
                    if (setting.insert_type == 1) {
                        insert($(elements).eq(i), setting.fadein && fadein);//插入元素
                    } else if (setting.insert_type == 2) {
                        insert2($(elements).eq(i), i, setting.fadein && fadein);//插入元素
                    }
                }
            });
        }
        function public_render(elems) {//ajax得到元素的渲染接口
            render(elems, true);
        }
        function insert($element, fadein) {//把元素插入最短列
            if (fadein) {//渐显
                $element.css('opacity', 0).appendTo(waterfall.$columns.eq(calculateLowest())).fadeTo(setting.fadein_speed, 1);
            } else {//不渐显
                $element.appendTo(waterfall.$columns.eq(calculateLowest()));
            }
        }
        function insert2($element, i, fadein) {//按序轮流插入元素
            if (fadein) {//渐显
                $element.css('opacity', 0).appendTo(waterfall.$columns.eq(i % waterfall.column_num)).fadeTo(setting.fadein_speed, 1);
            } else {//不渐显
                $element.appendTo(waterfall.$columns.eq(i % waterfall.column_num));
            }
        }
        function calculateLowest() {//计算最短的那列的索引
            var min = waterfall.$columns.eq(0).outerHeight(), min_key = 0;
            waterfall.$columns.each(function(i) {
                if ($(this).outerHeight() < min) {
                    min = $(this).outerHeight();
                    min_key = i;
                }
            });
            return min_key;
        }
        function getElements() {//获取资源
            $.waterfall.load_index++;
            return setting.getResource($.waterfall.load_index, public_render);
        }
        waterfall._scrollTimer = null;//延迟滚动加载计时器
        function onScroll() {//滚动加载
            clearTimeout(waterfall._scrollTimer);
            waterfall._scrollTimer = setTimeout(function() {
                var $lowest_column = waterfall.$columns.eq(calculateLowest());//最短列
                var bottom = $lowest_column.offset().top + $lowest_column.outerHeight();//最短列底部距离浏览器窗口顶部的距离
                var scrollTop = document.documentElement.scrollTop || document.body.scrollTop || 0;//滚动条距离
                var windowHeight = document.documentElement.clientHeight || document.body.clientHeight || 0;//窗口高度
                if (scrollTop >= bottom - windowHeight) {
                    render(getElements(), true);
                }
            }, 100);
        }
        function onResize() {//窗口缩放时重新排列
            if (calculateColumns() == waterfall.column_num)
                return; //列数未改变，不需要重排
            var $cells = waterfall.$container.find(setting.cell_selector);
            waterfall.$columns.remove();
            waterfall.$columns = creatColumn();
            render($cells, false); //重排已有元素时强制不渐显
        }
}));